Finishing process and fabric



Patented Sept. 14, 1954 Ul'iED STATES E ATENT OFFICE FINISHING PROCESSAND FABRIC N 0 Drawing. Application February 18, 1952, Serial No.272,263

19 Claims.

This invention is concerned with a finishing process for textilefabrics, especially cotton fabrics, and with the fabrics so produced.More particularly the invention relates to a process for producinghighly permanent, lustrous, glazed and embossed effects upon suchfabrics.

Heretofore the art has sought to produce effects of the type hereattained by impregnating the fabric with a thermosetting resin and thencalendering or glazing the fabric at elevated temperatures, the resinnormally becoming cured or set an incident of the calendering orglazing. The finishes so produced have a number of defects. Thus, whenthe resin employed contains nitrogen, as is generally the case, e. g.,urea, thiourea, mela mine, etc, the finish is at least to some extentchlorine retentive. As a consequence, when the fabric is laundered andno anti-chlor rinse is used, the fabric retains chlorine taken from anybleaching reagents which may have been present, with the result that onlater ironing, the fabric becomes yellowed and weakened. The yellowingmay be noticeable, even when the fabric is dyed, unless the shade isquite dark. It is virtually impossible, using one of thenitrogen-containing resins, to produce a finished white fabric whichwill remain white. In any case, the permanency to washing and/or drycleaning of the fabric may be unsatisfactory.

The present invention has as an object to provide a process givingsatisfactory finishes without '18 of resins or through the use of resinsin reduced amounts, whereby the indicated adverse effects are eithereliminated or substantially reduced. Another object is to provide afinishing treatment which does not result in any serious weakening ordeterioration of the component yarns of the treated fabric. Stillanother object is to give added permanence to finishes imparted by calndering.

The process herein is distinguished, inter alia, in that before thefabric is mechanically treated as determined by the desired finish,there is deposited in and on the yarns thereof a readily deformablecellulosic material. Following the mechanical treatment, the fabric isimpregnated with formaldehyde and/or a formaldehyde donor, i. e., aformaldehyde-yielding substance, and with a material adapted to catalyzethe reaction of cellulose and formaldehyde, the impregnated fabric beinglater heated as necessary to effect the indicated reaction.

When there is used in the practice of the process a cellulosic substancefrom which cellulose is readily precipitated or regenerated, as ispreferred, the fabric is subjected at some stage to a treatment adaptedto bring about conversion of the substance or its residuum to cellulose.

It will be understood that the nature of the mechanical treatment variesdepending upon the surface characteristics sought. In general, suchcalendering operations as friction and chase calendering arecontemplated, along with embossing, schreinering, glazing, beetling, andthe like, all of which are designated in this description and in theclaims as calendering.

It has been found that the deposited cellulosic material, which remainspermanently or substantially permanently on the fabric, enablesattainment of a better, more durable calendered or embossed finish withrelatively little mechanical damage to the yarns of the treated fabric.In fact, by reason of the presence of the deposited cellulosic material,the yarns in some cases actually may have a greater tensile strengthafter the calendering treatment than before.

In carrying out the process as practiced according to one of twopreferred schemes, the parent fabric is initially impregnated with anaqueous solution of cellulose xanthate and is thereafter subjected tothe action of an acid, sulfuric acid, for example, to regenerate thecellulose from the xanthate. Following this operation, the fabric iswashed and preferably while still moistened at least to a slight extentis subjected to the mechanical treatment, most usually a calenderingoperation. Thereafter the fabric, either in the wet or dry state, isimpregnated with formaldehyde and a catalyst, ammonium thiocyanate forinstance, and passed through a hot air curing chamber in which it ismaintained at a temperature of the order of 350 F. for a few minutes tobring about reaction between the cellulose and the formaldehyde.Although the nature of such reaction is not definitely known, that thereis a definite reaction is conclusively established by the fact that theaffected cellulose is insoluble or at least has a reduced solubility incopper-ammonia solution.

Using the other of the two preferred schemes, the procedure is as abovedescribed except that not until after the mechanical treatment is thefabric treated in an acid bath to convert the deformed cellulosexanthate to regenerated cellulose. Alternatively, instead of decomposingresidual cellulose xanthate prior to curing, the treatment in the acidbath may be delayed until after the curing operation.

Insteadof solutions or dispersions of cellulose xanthate, othersolutions or dispersions from which cellulose can be regenerated orprecipitated, so as to become a permanent or substantially permanentpart of the fabric, may be employed in the practice of theinvention--for example, cellulose in cuprammonium solution, or incertain quaternary solvents. In addition there are certain cellulosecompounds, dispersible in and precipitatable as such from aqueous, oraqueousalkaline media, which can be similarly employed, e. g. celluloseethers of a suitable degree of etherification, such as the ethyl orpropyl ethers, and hydroxy ethers such as the ethyl hydroxy ether ofcellulose. The terms dispersion and dispersed as used in thespecification and claims are intended to include all of the foregoing,whether they be true solutions or colloidal dispersions. Thosecellulosic materials generally applied in the arts in solution inorganic solvents are unsuited for the purposes of the invention. As ex-'emplary of this class of materials, nitrocellulose may be cited.

Formaldehyde donors which may be employed in place of formaldehydeitself in the practice of the invention include hexamethylenetetramine,certain formals, paraform and the like. Also there may be used resinssynthesized in part from formaldehyde which, under the con ditions ofthe heating and curing steps of the process, are capable of providingformaldehyde for reaction with the cellulose. These formaldehyde-resinsare therefore formaldehyde donors and such resins are prepared, as isWell known in the art, by reacting formaldehyde with suitable materials,for example, urea, thiourea, a ketone such as acetone, or melamine ornumerous other materials. Particularly preferred for this purpose arewater-soluble precondensates or low polymers of methylolurea, methylolmelamine and the like. It is recognized that such resins are of theclass noted in the forepart hereof as tending through chlorine retentionto cause discoloring of the fabric from ironing. However, in the presentcase the resins can be employed in relatively small amounts so that suchundesirable effects are mitigated. The principal advantage residing inthe use of formaldehyde-resins as formaldehyde donors goes to the factthat the finish, in addition to being highly durable, is rendered moreresistant to creasing. For this effect it is obviously necessary thatthe resin be used in sufficient quantity that all of it is not exhaustedin providing formaldehyde for reaction with the cellulose. We may, ofcourse, employ such resins in an impregnating bath additionallycomprising in any desired ratio either formaldehyde added as such or aformaldehyde donor other than a formaldehyde-resin. Also resins of arelative high state of polymerization may be used in conjunction withthe soluble low polymers.

Many substances are known to catalyze the reaction of formaldehyde andcellulose. These are in general acidic substances or substances whichbecome acidic at the elevated temperatures at which the reaction takesplace, e. g., tartaric acid, lactic acid, boric acid, various sulfonicacids, oxalic acid, acetic acid, formic acid, salts such as ammoniumthiocyanate, ammonium acid phosphate, ammonium chloride and the like.Catalytic properties have also been attributed to essentially neutralsalts, especially inorganic salts, and to alkaline substances such ascaustic soda, alkali carbonates and the like. A number of the foregoingsubstances also catalyze the polymerization of the formaldehyde-resinsjust discussed.

Most of the mechanical treatments here contemplated are carried out atan elevated temperature. For example, in calendering cotton fabriccontaining cellulose xanthate or cellulose regenerated from cellulosexanthate the calender rolls are generally maintained at a temperature ofthe order of 350 to 425 F. The pressure exerted by the rolls will varydepending on the fabric and the finish desired. Usually, however, thetotal nip pressure is between 10 and 60 tons. Rolling, chasing, orembossing calenders as well as friction calenders are, of course,applicable to the invention, preferred practices of which areillustrated by the following examples, which are not to be taken as inany way limitative of the scope of the invention.

Example 1 A bleached, cotton fabric counting 80 x 80, Weighing 4.0 yardsper pound, and having a grey width of 37 inches was impregnated in amangle with an aqueous cellulose xanthate composition containing 3.0%cellulose (present as the cellulose in the xanthate), 2.5% sodiumhydroxide and 2.0% of a substantive, non-ionic softener. In addition,the bath contained products of the xanthation reaction.

The pick-up from the bath was about The impregnated fabric was runwithout drying into a bath of 10% sulfuric acid in which the xanthatewas decomposed leaving regenerated cellulose in and on the fabric. Theacidtreated fabric was thoroughly washed first with hot and then withcold water, squeezed off and partially dried by passing through a heatedtenter frame at near grey width. The fabric as it emerged from the framecarried about 10 to 15% moisture and was immediately passed three timesthrough a friction calender heated to 400 F. and exerting a total nippressure of tons. Following this operation, the calendered fabric wasimpregnated in a mangle with a 5% aqueous solution of formaldehydecontaining 03% ammonium thiocyanate. The pick-up was about 50%. Theformaldehyde-impregnated material was substantially dried by passing itthrough a tenter frame heated to about 260 F. Thereafter it was passedthroughahot air curing chamber in which the fabric was maintained at 350F. for two minutes. The cured fabric was sub- J'ected to the action ofan aqueous scouring bath (containing 0.5% sulfonated higher fattyalcohol detergent, and 0.2% ammonia) and then thoroughly washed in hotand cold water, respectively. The framed finished fabric wascharacterized by a rather high gloss or glaze, yet it had a pleasinglysoft and and good tensile strength. Upon repeated washing the fabricretained its glossy finish and pleasing hand substantially unimpaired.

Example 2 A bleached cotton fabric counting x 92. weighing 3.50 yardsper pound, and having a grey width of 40 inches was impregnated in amangle with an aqueous cellulose xanthate composition, made bydissolving cellulose xanthate (prepared from well aged alkali cellulose)in water, and then neutralizing with dilute acid to a pH of about '7under conditions avoiding any permanent coagulation or precipitation ofthe cellulose xanthate. The composition had the following formulation,ignoring products of the xanthation reaction and reaction products fromthe neutralization Per cent by weight Cellulose (present in thexanthate) 2.0 Substantive, non-ionic softener 2.0

The pick-up by the fabric from the bath was about 50 The impregnatedfabric was conveyed through a heated tenter frame at near grey width.The fabric as it emerged from the frame carried about to moisture andwas immediately passed through an embossing calender heated to about 405F.

Following the calendering, the fabric was run into a bath of 10%sulfuric acid in which any remaining xanthate was decomposed, leavingmechanically deformed regenerated cellulose in and on the fabric. Theacid-treated fabric was thoroughly washed first with hot and then withcold water, squeezed, and dried by passage through a heated tenter frameat near grey width. After this operation, the fabric was treated with a5% aqueous solution of formaldehyde containing 0.3% ammoniumthiocyanate. The picleup from the formaldehyde bath was about 50%. Theformaldehyde-impregnated material was substantially dried by passing itthrough a tenter frame heated to about 260 F. Thereafter it was passedthrough a hot air curing chamber in which the fabric was maintained atabout 350 F. for two minutes. The cured fabric was secured and washedand finished as in Example 1. The finished fabric had a well defined,three dimensional embossed pattern which was fast to washing.

Example 3 The treatment was the same as in Example 2 through theembossing operation. However, the embossed fabric, without anyintervening operation was treated with a 5% aqueous solution offormaldehyde containing 0.3% ammonium thiccyanate and enough dihydrogenammonium phosphate to neutralize any residual alkali in the cellulosexanthate. ihe pick-up from the modified for-.1aldehyde bath was about196%. The formaldehyde impregnated material was substantially dried bypassing it through a tenter frame heated to about 256 F. Thereafter, itwas conveyed through a hot air curing chamber (341? F. for two minutes).lThe cured fabric was run into a bath of 19% sulfuric acid in which anyremaining xanthate was decomposed leaving deformed, formalizedregenerated cellulose in and on the fabric. Subsequently, the curedfabric washed and then scoured, washed again, and fun ished as inExample 1. The finished fabric had properties in general similar to thefabric of Example 2.

Example 4 Example 5 In a modification of the process as illustrated byExample 1, the treatment may conform such example through thecalendering operation.

Thereafter, in lieu of impregnating the fabric as described in suchexample, the fabric may be impregnated by running the same through abath containing 10% melamine-formaldehyde resin (water-soluble lowpolymer) and 0.3% isopropylamino-hydrochloride. On subsequent passage ofthe impregnated fabric through the h t air curing chamber (350 F. fortwo minutes), some formaldehyde is freed from the resin for reactionwith the cellulose while the undecompcsed por tion polymerizes to confercrease resistance to the fabric.

Calendaring or embossing the xanthate-im pregnated fabric with thecellulose xanthate sub stantially undecomposed, or only partiallydecomposed gives added permanence to the calendered and embossed effectsobtained. While it is desirable to substantially neutralize thecellulose xanthate, partially neutralized xanthate, or evenunneutralized xanthate is operable. To neutralize the cellulose Xanthatereaction mixture one may use for example dilute mineral acids, organicacids, or other acidic substances.

As is well known in the art, cellulose xanthate is readily prepared byreacting carbon bisulfide with suitably aged alkali cellulose anddispersing the reaction product in water, if with the aid of a small antof caustic so. lfhe amount of regenerated cellulose, or cellulosicmaterial added to the fabric may vary with the fabrics treated and theeffects but will usually be within the ll its of a few tenths to severalper cent-5 to 1d per cent or higher. lifter impregnation with celluloseanthate, the fabric is preferably not dried if the regeneration orprecipitation of the cellulose is to follow immediately. In any case thefabric is preferably not completely dried prior to calendering. Thefabric, after the calendering step, may be dried at a high temperature,for example 358 but it is usually adequate to dry at normaltemperatures, for example 250 F. prior to the formaldehyde impregnation.In the impregnation steps the liquid pi .:-up may vary widely butusually will be between. the limits of somewhat less than 53 per cent upto 2G8 cent or higher. time and temperature re quired to bring aboutreaction of the formaldehyde and the cellulose and/or the cell losicJana-- terial chiefly depend on the strength of the catalyst, and theamount of catalyst emplo; Usually, the concentration of the formaldehydewill lie within the range of from one to 15%, depending on the structurecomposition of the fabric, the finish desired, and other considerations.

While any suitable softener can be employed at one or more stages of theprocess, it is preferred to use a substantive softener such as anon-ionic softener for example, an alkaline persion of a substitutedfatty amide, or an anionic softener especially for admixture withcellulose xanthate solution.

It is to be understood that the present invention may be applied notonly to cotton fabrics, but also to fabrics of linen, cellulosic rayespecially spun rayons, and to their mixtures with cotton.

Having thus described and illustrated our in vention, what We claim is:

1. Method of finishing cellulosic textile fabrics comprising depositingin and on the yarns of the fabric from an aqueous medium a mechanicallydeformable cellulosic material dispersed in medium, said cellulosicmaterial being reactable with formaldehyde, thereafter calendering thefabric to provide the desired finish while the fabric is free fromacidic catalytic materials, thereafter impregnating the calenderedfabric with at least one substance of the class consisting offormaldehyde and formaldehyde donors and With a catalyst for thereaction of formaldehyde and the cellulosic material, and finallyheating the fabric to produce such reaction.

2. Method of finishing cellulosic textile fabrics comprisingimpregnating the fabric with cellulose xanthate from an aqueous medium,thereafter treating the impregnated fabric with a cellulose-regeneratingagent, thereafter calendering the sotreated fabric to provide thedesired finish agent, thereafter impregnating the fabric with 1formaldehyde and an acidic catalyst for the reaction of formaldehyde andcellulose and finally heating the fabric to a temperature and for aperiod of time effective to bring about such reaction.

4. Method of finishing cellulosic textile fabrics comprisingimpregnating the fabric with cellulose xanthate from an aqueous medium,thereafter calendering the so-treated fabric to provide the desiredfinish while the fabric is free from acidic catalytic materials,thereafter impregnating the calendered fabric with formaldehyde and anacidic catalyst for the reaction of formaldehyde and cellulose,thereafter heating the fabric to a temperature and for a period of timeeffective to bring about the indicated reaction, and subsequentlysubjecting the fabric to treatment with a cellulose-regenerating agent.

5. Method of finishing cotton fabrics comprising impregnating the fabricwith cellulose xanthate from an aqueous medium, thereafter treating theimpregnated fabric with acid to regenerate cellulose from the xanthate,thereafter calendering the so-treated fabric to provide the desiredfinish while the fabric is free from acidic catalystic materials, thefabric as introduced to the calendering being in a moistened condition,thereafter impregnating the calendered fabric with formeldehyde and anacidic catalyst for the reaction of the formaldehyde and cellulose andfinally heating the fabric to a temperature and for a period of timeefiective to bring about such reaction.

6. Method according to claim 5 where the calendering consists of a hotcalendering operation.

'7. Method of finishing cellulosic textile fabrics comprisingimpregnating the fabric with substantially neutral aqueous cellulosexanthate solution, thereafter calendering the so-treated fabric toprovide the desired finish while the fabric is free from acidiccatalytic materials, the fabric as introduced to the calendering beingin a moistened condition, thereafter treating the calendered fabric witha cellulose-regenerating agent, thereafter impregnating the fabric withformaldehyde and an acidic catalyst for the reaction of formaldehyde andcellulose and finally heating the fabric to a temperature and for aperiod of time effective to bring about such reaction.

8. Method according to claim 7 where the calendering consists of a hotcalendering operation.

9. Method of finishing cotton textile fabrics comprising impregnatingthe fabric with a substantially neutral aqueous cellulose xanthatesolution, thereafter calendering the so-treated fabric to provide thedesired finish while the fabric is free from acidic catalytic materials,the fabric as introduced to the calendering being in a moistenedcondition, thereafter impregnating the calendered fabric withformaldehyde and an acidic catalyst for the reaction of formaldehyde andcellulose, thereafter heating the fabric to a temperature and for aperiod of time effe tive to bring about the indicated reaction, andsubsequently subjecting the fabric to treatment with acellulose-regenerating agent.

10. Method according to claim 9 where the calendering consists of a hotcalendering operation.

11. Method of finishing a cellulosic textile fabric comprisingdepositing in and on the yarns of the fabric from an aqueous medium amechanically deformable cellulosic material dispersed in said medium,said cellulosic material being reactable with formaldehyde, thereaftercalendering the fabric to provide the desired finish while the fabric isfree from acidic catalytic materials, thereafter impregnating thecal-2ndered fabric with a formaldehyde-resin and an acidic catalyst, andfinally subjecting the impregnated fabric to heat whereby a portion ofthe resin becomes more completely polymerized to impart creaseresistance to the fabric, the remaining portion providing formaldehydefor reaction with the cellulosic material.

12. Method according to claim 11 where the cellulosic material depositedon the fabric is cellulose xanthate and the fabric is treated at somestage to convert the cellulose xanthate to regenerated cellulose.

13. Method of finishing cellulosic textile fabrics comprisingimpregnating the fabric with cellulose xanthate from an aqueous medium,thereafter treating the impregnated fabric with a cs.lulose-regenerating agent, thereafter calendering the so-treated fabricto provide the desired finish while the fabric is free from acidiccatalytic materials, thereafter impregnating the calendered fabric witha formaldehyde-resin and acidic catalyst, and finally heating the fabricto a temperature and for a period of time effective to bring aboutpolymerization of the resin reaction of formaldehyde with the cellulose.

14. Method of finishing cotton fabrics comprising impregnating thefabric with cellulose xanthate from an aqueous medium, thereaftertreating the impregnated fabric with acid to regenerate cellulose fromthe xanthate, thereafter calendering the so-treated fabric to providethe desired finish while the fabric is free from acidic catalyticmaterials, the fabric as introduced to the calendering being in amoistened condition, thereafter impregnating the calendered fabric witha formaldehyde-resin and an acidic catalyst, and finally heating thefabric to a temperature and for a period of time effective to bringabout 9 polymerization of the resin and reaction of formaldehyde withthe cellulose.

15. Method of finishing cellulosic textile fabrics comprisingimpregnating the fabric with substantially neutral aqueous cellulosexanthate solution, thereafter calendering the so-treated fabric toprovide the desired finish while the fabric is free from acidiccatalytic materials. the fabric as introduced to the calendering beingin a moistened condition, thereafter treating the calendered fabric witha cellulose-regenerating agent, thereafter impregnating the fabric witha formaldehyde-resin and an acidic catalyst, and thereafter finallyheating the fabric to a temperature and for a period of time effectiveto bring about polymerization of the resin and reaction of formaldehydewith the cellulose.

16. A textile fabric prepared by the method of claim 1.

17. A textile fabric prepared by the method of claim 2.

- 10 18. A textile fabric prepared by the method of claim 11.

19. A textile fabric prepared by the method of claim 13.

References Cited in the file of this patent UNITED STATES PATENTS

1. METHOD OF FINISHING CELLULOSIC TEXTILE FABRICS COMPRISING DEPOSITINGIN AND ON THE YARNS OF THE FABRIC FROM AN AQUEOUS MEDIUM A MECHANICALLYDEFORMABLE CELLULOSIC MATERIAL DISPERSED IN SAID MEDIUM, SAID CELLULOSICMATERIAL BEING FEACTABLE WITH FORMALDEHYDE, THEREAFTER CALENDERING THEFABRIC TO PROVIDE THE DESIRED FINISH WHILE THE FABRIC IS FREE FROMACIDIC CATALYTIC MATEQRIALS, THEREAFTER IMPREGNATING THE CALENDEREDFABRIC WITH AT LEAST ONE SUBSTANCE OF THE CLASS CONSISTING OFFORMALDEHYDE AND FORMALDEHYDE DONORS AND WITH A CATALYST FOR THEREACTION OF FORMALDEHYDE AND THE CELLULOSIC MATERIAL, AND FINALLYHEATING THE FABRIC TO PRODUCE SUCH REACTION.